Various designs of reciprocating plunger well pumps have been developed of the general type wherein the pump is mounted at the lower distal end of an elongated well tubing string, includes a reciprocating plunger or piston connected to an elongated rod extending to an actuating mechanism at the earth's surface and also includes a cylinder in which the plunger reciprocates to displace fluid from a plunger cavity and controlled by cavity inlet and discharge valves mounted on the cylinder and on the plunger, respectively.
In spite of the relatively highly developed state of the art in reciprocating plunger well pumps, certain problems in the operation of these pumps persist. In particular, conventional reciprocating plunger well pumps used in water wells, for example, are often burdened with rapid corrosion, in spite of the development of relatively corrosion resistant materials, and are prone to early failure or unexpected wear as a consequence of entrainment of solid particulates in the pumped fluid and the formation of wear-causing solids particles resulting from the above-mentioned corrosive operating conditions of such pumps.
Efforts to eliminate the above-mentioned problems while providing a well pump which is inexpensive to manufacture and is reliable in operation have not been entirely successful and further improvements in such pumps have long been sought. It is to these ends that the present invention has been developed.